This assessment report, referred to as the HOLAS report, is the fi rst attempt to conduct a Holistic Assessment of the ecosystem health of the Baltic Sea. It is a product of the Helsinki Commission (HELCOM), the intergovernmental body composed of the Baltic Sea coastal states and the EU, to implement the Convention on the Protection of the Marine Environment of the Baltic Sea Area, 1992 (the Helsinki Convention). The assessment serves two key purposes. Firstly, it presents an integrated assessment of the ecosystem health of the Baltic Sea as well as thematic assessments of ‘eutrophication status’, ‘biodiversity status’ and ‘hazardous substances status’. Secondly, it sets a baseline for evaluating the effectiveness of the implementation of the measures of the HELCOM Baltic Sea Action Plan that was adopted in 2007. Furthermore, the Initial Holistic Assessment is also a regional contribution to the initial assessment according to the Marine Strategy Framework Directive (MSFD) for those HELCOM Contracting Parties that are also EU Member States. This assessment also covers a number of aspects of Good Environmental Status, as described by the qualitative descriptors of Annex III of the MSFD, including eutrophication, contamination by hazardous substances and biodiversity aspects. It will facilitate the work of the EU Member States of HELCOM in implementing the requirements of the Directive that are related to those descriptors, especially the development of the initial assessment, targets and associated indicators for Good Environmental Status that are due in June 2012. Moreover, it provides input to the overall requirement of the Directive for coordination and cooperation among the countries within a marine region. The HOLAS report is supplemented by thematic assessments which can be downloaded at http://www.helcom.fi/BSAP_assessment/en_GB/main/